Sure thing kieren I'll do my best
The standard sump on our cars does not contain a proper baffle.
This means hard cornering and lateral g's applied to the car will cause oil to slosh around and make it's way out of the sump, and back into the "block" or crank case
Because of the unique design of the boxer motor, the crank case actually encompasses ALL the rotating assembly (crank, rods, main caps etc). The crank being in the centre of the case halves here
So cos of my "awesome" driving at the track yesterday, oil has managed to find its way into the crank case, in relatively large amounts.
Now consider that the crank case breather pipe (which would ordinarily connect to a hose running back to the inlet tract, but in my car runs to the catch can) - consider that this breather pipe regulates the amount of oil in the crank case. Usually this would only be equivalent to I dunno say 20-100ml of excess oil being sprayed up from the sump or through the various galleries. In fact most of the time this would be a mist. If you undo the hose on this pipe you will see it spurting "pulses" of oil mist (not streams or flow of oil). This is because as I said it shouldn't have loads of oil to vent, and thus with the combustion chamber pressures which escape the lower piston oil control ring (which again shouldn't be much in a healthy motor, but enough to vent the excess oil mist buildup ), it pushes a spray of oil out
Now in my instance, all the oil splashing up from the sump has been spraying up into the catch can. Thus why it wouldn't have done anything to prevent what I saw today. The breather was still going to get rid of that excess oil that shouldn't have been there
Could the excess oil have caused damage - short answer yes. Did it? Well I hope not
Reason it could cause damage is oil getting to places it really shouldn't (remembering what I said above that the crank case should only see a film or mist of oil every now and again). Also, if enough oil came up so as to reach the rods / pistons, then it can be whipped up and thus pressurizing (not good for oil flow and lubrication), and also could've damaged oil control rings in the cylinder, thus making them ineffective in future and causin the motor to chew oil or worse still, stuff a ring (bye bye motor)
Thus why catch can wouldn't have helped
Good news is as follows:
- the oil has stopped pissing out of the crank case breather hose (for now)
- this tells me it was just doing its job and getting rid of excess oil
- the motor doesn't seem to be chewing oil (butthat will need monitoring and it's too early to tell yet)
- the remaining oil in the sump has not been "whipped" (it would've changed colour)
- motor still runs fine (and scared the shit out of a 04sti wrx onthe way home top

)
Sorry for the long post
I'm an insomniac and did my best to explain
Mick